This invention relates to new, water-soluble or water-dispersible resinous sulphur or phosphorus-containing salts, to a process for their preparation, compositions containing them, and a method of coating surfaces with such compositions.
To obtain a corrosion-resistant coating for metal containers it is conventional to coat the metal surface with a crosslinkable resin formulation dissolved in an organic solvent and then to heat the coating to evaporate the solvent and to crosslink the resin. Crosslinking the coating converts it into a tough, adherent, flexible, and protective film. During heating, the solvent is usually evaporated into the atmosphere. Since organic solvents are relatively expensive, inflammable, and usually environmentally objectionable, there exists a need for coatings which may be applied using minimal proportions of such solvents, particularly useful being coating compositions which contain a high proportion of water.
We have now found that stable aqueous compositions which cure to give coatings having excellent mechanical properties and chemical resistance may be prepared from new resinous sulphur or phosphorus-containing salts. These salts are prepared from a phenol-terminated resin by a Mannich reaction with an aldehyde and an aminosulphonic acid or an aminophosphonic acid followed by partial or complete neutralisation of the acid group or groups introduced by this reaction. The salts may be used with an aminoplast, a phenol-formaldehyde resin, or a blocked polyisocyanate as aqueous surface coating compositions. In certain circumstances the addition of such a coreactant is not, however, necessary.
The use of a Mannich reaction to obtain water-soluble coating compositions from epoxides or phenols has already been disclosed.
For example, in U.S. Pat. No. 4,188,312 there are described coating compositions containing the reaction product of an epoxide resin (i.e., a compound having, per average molecule, more than one 1,2-epoxide group) with a Mannich base and an alkenylphenol. This Mannich base is the reaction product of a polyhydric polynuclear phenol, a secondary amine containing at least one hydroxyalkyl group, and formaldehyde. U.S. Pat. No. 4,189,450 describes coating compositions prepared from an epoxide resin and a Mannich base derived from a condensed phenol, a secondary amine containing at least one hydroxyalkyl group, formaldehyde, and a butadiene or isoprene homo- or co-polymer containing phenolic groups. The products are epoxide-free and are water-soluble in their protonated form.
British Patent Specification No. 1,428,835 describes a cationic polymer prepared by the aminomethylation of a p-hydroxystyrene polymer, using formaldehyde and a secondary amine which either has alkyl, alkenyl, or aromatic groups attached to the nitrogen atom or is a heterocycle having 4 to 6 carbon atoms in the ring. The product may be quaternised or an acid addition salt may be formed from it.
U.S. Pat. Nos. 4,000,116 and 4,014,955 describe crosslinked macromolecular polyethers prepared by reaction of a Mannich base with a polyepoxide, followed by polyquaternisation, or by reaction with a compound containing both a chlorine, bromine, or iodine atom bonded to a hydrocarbon radical and at least one epoxide group. The Mannich bases are prepared from a monomeric bisphenol and the amines used are dialkylamines or morpholine.
British Patent Specification No. 1,457,932 describes epoxide group-free polymers which are prepared by reaction of a Mannich base with an epoxide resin, followed by salt formation. The Mannich base, containing one or more cationic hydroxyalkylaminomethyl groups attached to each aromatic ring, is prepared by reaction of a bisphenol, a hydroxyl group-containing secondary amine, or a mixture of such an amine with another primary or secondary amine, and formaldehyde. The resin therefore contains these cationic groups attached to each ring in as many residues derived from the Mannich base as are in the molecular chain.
In the processes described in other patent specifications of this type, polymeric bisphenols which are reaction products of monomeric bisphenols and epoxide resins are reacted with formaldehyde and a hydroxyalkyl group-containing secondary amine to produce polymeric Mannich base bisphenols. For example, in the process described in U.S. Pat. No. 3,994,989 such a polymeric bisphenol is reacted in admixture with a monomeric bisphenol; in the process described in British Patent Specification No. 1,563,917 the polymeric bisphenol is reacted alone or in admixture with a monomeric bisphenol. The polymeric Mannich base bisphenols have cationic hydroxyalkylaminomethyl groups attached to only one aromatic ring at each end of the chain. However, these polymeric Mannich base bisphenols are not used directly in coating compositions, but are further advanced by reaction with epoxide resins to produce bisphenols of yet higher molecular weight. In the latter, the cationic groups would be attached to the terminal aromatic rings of the residues derived from the polymeric Mannich base bisphenols not only at the ends of the molecular chain of the final product but also wherever those residues occur in the remainder of the chain.
In U.S. Pat. No. 3,936,399 phenolic chelating resins are described which are prepared by a Mannich reaction of a phenol, iminodiacetic acid, and an aldehyde, and polycondensing the resultant product with an aldehyde. The polycondensed resin has highly selective adsorbability to heavy metals. There is no indication that the intermediate material, prepared by the Mannich reaction, would have any other utility.
West German Offenlegungsschrift No. 1 445 535 describes the preparation of alkali-soluble condensation products by reacting, in alkaline, acid, or neutral aqueous medium, (a) a phenol or naphthol, (b) formaldehyde or a formaldehyde-generating substance, (c) a 5- or 6-membered heterocyclic compound, and (d) a mononuclear aromatic carboxylic or sulphonic acid, optionally containing hydroxyl or amino groups, an aryloxy fatty acid, or an aliphatic polycarboxylic acid. Components (a) and (b) are reacted first and the product is reacted in any order with (c) and (d), and optionally with more formaldehyde. The phenol (a) may be a bisphenol such as bisphenol A. Suitable heterocyclic compounds (c) include carbazole, quinoline, and pyrrolidone. Suitable aminosulphonic acids for use as (d) are sulphanilic acid and metanilic acid. The condensation products are said to be useful in carbon paper waxes, lithographic compositions, and as laking components for basic dyes in flexographic inks.
West German Offenlegungsschrift No. 2 353 642 discloses binders for heat-hardenable moulding compositions comprising (a) a phenolformaldehyde condensation product modified by an aminocarboxylic acid or aminosulphonic acid and (b) a hardener. The condensation product (a) can be obtained by heating 2-6 mols of phenol, 1 mol of amino acid, and 0.5-1 mol of formaldehyde per mol of the combined phenol and amino acid. The condensation can be effected either without a catalyst or in the presence of an alkali, to give a product similar to a novolak. Aminosulphonic acids said to be suitable are taurine, methyltaurine, sulphanilic acid, and aminopropylsulphonic acid. The product is soluble in aqueous alkali and is especially suitable for use in foundry moulding compositions. Hexamethylenetetramine is specified as hardener.
U.S. Pat. No. 4,317,757 discloses water-thinnable, heat-curable binders for coatings, prepared by reacting a polyglycidyl ether of a polyhydric phenol with neutralised sulphanilic acid in a ratio of 0.9 to 1.1 NH equivalents per epoxy equivalent. The binders are said to be particularly suitable for use in aqueous can lacquers, together with aminoplasts or phenoplasts as crosslinking agents. The sulphanilic acid is preferably neutralised with an alkali metal hydroxide or a tertiary amine. The reaction between the epoxide resin and the neutralised sulphanilic acid is preferably carried out at 100.degree.-130.degree. C. for 2-7 hours. In the Examples, epoxide resins having molecular weights of 950 and 370 respectively are used and the reactants are heated at 124.degree. C. for 5 hours.
U.S. Pat. No. 4,332,709 describes water-thinnable binders suitable for use in aqueous can lacquers. They are prepared by reacting a polyglycidyl ether of a polyhydric phenol with an aliphatic amino acid in which at least 50% of the acid groups have been neutralised with a base, in a ratio of 0.7 to 1.2 NH equivalents per epoxy equivalent. Suitable amino acids are said to include carboxylic acids and sulphonic acids, but no specific aminosulphonic acids are suggested. Suitable neutralising bases are said to be alkali metal hydroxides, tertiary amines, and quaternary ammonium hydroxides. The epoxide resin is preferably heated with the neutralised amino acid at 90.degree.-100.degree. C. for about 15 minutes. The binders may be included in aqueous coating compositions together with aminoplasts or phenolic resins as crosslinking agents.
British Patent Specification No. 2,083,044 discloses water-dispersible, modified epoxide resins having a terminal amphoteric aminosulphonate group of formula --CH.sub.2 --C(R.sub.1)OH--CHR.sub.2 --NH(R.sub.3)--R.sub.4.sup.+ --SO.sub.3.sup.-, where R.sub.1 and R.sub.2 represent a hydrogen atom or a methyl group, R.sub.3 represents a hydrogen atom, or an alkyl group optionally substituted with higher alkylsulphinyl or higher alkanoyloxy, and R.sub.4 represents alkylene optionally substituted with 2-hydroxyethyl. The modified resins are obtained by reacting epoxide resins having a terminal glycidyl group with an aminosulphonate R.sub.3 NHR.sub.4 SO.sub.3 M where M is a cation. Preferred aminosulphonates are sodium and potassium salts of taurine, N-(alkyl)taurines, and 6-aminohexane-1-sulphonic acid. Preferably, at least 20% of the glycidyl groups are converted into the aminosulphonate groups. Suggested uses for the modified resins include use in aqueous coating compositions, alone or together with an aminoplast.